In recent years, an IGCC (Integrated Gasification Combined Cycle) that includes a gasification unit and a combined power generation unit (combination of a gas turbine and a steam turbine) has been attracting attention. In the IGCC, since heavy metals and sulfur are almost completely removed from raw materials such as residues and coal that are used as fuel gas of the gas turbine in the course of producing synthetic gas, and clean fuel gas that is almost the same as natural gas is used, the environmental pollution load is reduced, and the IGCC is rated a high as an environmentally-friendly next-generation power plant.
In general, in this system, the raw materials such as the residues and the coal are gasified in a gasification furnace, harmful substances are removed in a gas treatment unit to produce clean fuel gas, and power is generated by a gas turbine using the fuel gas.
Furthermore, in this system, examples of a method of controlling the system include a gasification furnace lead control method in which a gasification furnace is controlled so as to produce fuel gas with production rate that is required in a power plant and a gas turbine is operated using the produced fuel gas; and a turbine lead control method in which a gas turbine is controlled to generate power in the required amount according to a power load and the synthetic gas required to operate the gas turbine is supplied from a gasification furnace. Currently, in order to rapidly cope with a change in the required power load; a cooperative control method in which the gasification furnace lead control method and the turbine lead control method are combined is adopted to perform a feed-forward control with respect to the gasification furnace.
The cooperative control method will be described hereinafter.
As shown in FIG. 3, an integrated gasification combined cycle is provided with a gasification process section 1 that gasifies fuel, and a combined power generation process section 2 that generates power by means of a gas turbine using the fuel gas supplied from the gasification process section 1.
In addition, a gasification process controller 5 to which a set value is transmitted from a gas pressure setting device 4 is connected to a fuel control valve 3 that is provided on a fuel feed line to the gasification process section 1, and the fuel control valve 3 is controlled using a control signal that is transmitted from the gasification process controller 5. The gasification process controller 5 computes a control value using a measurement signal that is transmitted from a gas pressure instrument 6 for measuring gas pressure in the gasification process section 1 and the set value that is obtained from the gas pressure setting device 4, and outputs a control signal to the fuel control valve 3.
Additionally, a power generation process controller 9 to which a set value is transmitted from a power load setting device 8 is connected to a gas control valve 7 that is provided on a gas feed line to the combined power generation process section 2, and the gas control valve 7 is controlled using the control signal that is transmitted from the power generation process controller 9. The power generation process controller 9 computes a control value using a measurement signal that is transmitted from a power output measurement 10 for measuring the power generation output of the combined power generation process section 2 and the set value that is obtained from the power load setting device 8, and outputs a control signal to the gas control valve 7.
In the integrated gasification combined cycle, in the case when the cooperative control system is performed, a feed-forward compensator 11 is provided, the set value is transmitted from the power load setting device 8 to the feed-forward compensator 11, and a feed-forward control signal is transmitted from the feed-forward compensator 11 to the fuel control valve 3. Accordingly, the feed rate of fuel that is supplied to the gasification process section 1 is increased or decreased according to a change in the required power load.
That is, in the cooperative control system, the gasification in the gasification furnace of the gasification process section 1 is rapidly controlled according to the change in the required power load.
The above-mentioned control technology is disclosed in, for example, Japanese Unexamined Patent Application, First Publication No. 2002-129910, Japanese Unexamined Patent Application, First Publication No. H07-234701, Japanese Patent Publication No. 2685341, and Japanese Unexamined Patent Application, First Publication No. H11-210412.